1. Field of the Invention
This invention relates to electrical measuring instruments and, more particularly, it pertains to the thermal type which is responsive to alternating quantities of electrical energy.
2. Description of the Prior Art
Thermal heater units of prior constructions have involved a variety of forms for measuring different electrical quantities. One known construction comprised heating means associated with a pair of bimetallic springs mounted on a shaft, one spring for rotating the shaft in one direction and another spring for rotating the shaft in the opposite direction. If one of the springs is heated more than the other, the difference in temperature causes the spring to twist the shaft harder than the other whereby the shaft advances a pointer on a scale.
Associated with the foregoing has been a heater comprised of a printed circuit which had a thichness of up to 0.005 inch which was too thin to handle during manufacture and assembly of the heater. As a result a high percentage of the heater was damaged and discarded during assembly.